1. Field of Invention
This invention relates to a fluid ejection printing apparatus.
2. Description of Related Art
Fluid ejection systems, such as ink jet printers, have at least one fluid ejection head that directs droplets of fluid towards a recording medium. Within the fluid ejection head, the fluid may be contained in a plurality of channels. Energy pulses are used to expel the droplets of fluid, as required, from orifices at the ends of the channels.
In a thermal fluid ejection system, such as a thermal ink jet printer, the energy pulses are usually produced using resistors. Each resistor is located in a respective one of the channels, and is individually addressable by voltage and/or current pulses to heat and vaporize the fluid in the channels. As a vapor bubble grows in any one of the channels, fluid bulges from the channel orifice until the pulse has ceased and the bubble begins to collapse. At that stage, the fluid within the channel retracts and separates from the bulging fluid to form a droplet moving in a direction away from the channel and towards the receiving medium. The channel is then re-filled by capillary action, which in turn draws fluid from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774, incorporated herein by reference in its entirety.
A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337, incorporated herein by reference in its entirety. That thermal ink jet printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel orifices in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary receiving medium as the carriage is moved in one direction. The receiving medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to or less than the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information.
Some fluid ejection systems, such as low cost ink jet printers, have paper advance subsystems that must operate on two opposing modes. The first mode is a high speed mode which maximizes the throughput of the receiving medium. The second mode is a high precision mode to accurately register the receiving medium.
Typically, a single motor with a single clutch and a single gear train is used to implement both the high speed mode and the high precision mode. The single motor is connected to the clutch and the gear train. The clutch and the gear train are also connected to a shaft with rollers. When the motor is activated, the rotational force of the motor is transferred through the clutch to the gear train. The gear train then transfers the rotational force to the shaft and roller. As the rollers rotate, the rollers advance the receiving medium.
However, a single clutch and a single gear train, when used to implement as both the high speed mode and the high precision mode, fail to accurately advance the paper. In particular, when a high precision mode is requested, the single clutch and gear train cannot accurately register the receiving medium.
This invention provides a receiving medium advancing mechanism having both a high speed subsystem and a high precision subsystem implemented using a simple low cost motor.
The invention separately provides two gear trains and two one-way clutches to provide two types of motion from a single motor.
In various exemplary embodiments of systems and methods according to this invention, a receiving medium advancing mechanism comprises a motor, a gear, a first one-way clutch and a second one-way clutch. When the motor rotates the gear in a first direction, the first one-way clutch, but not the second one-way clutch, is operated to advance the receiving medium in a first mode. When the motor rotates the gear in a second direction, the second one-way clutch, but not the first one way clutch, is operated to advance the receiving medium in a second mode. The first mode is a high advance mode while the second mode is high precision mode.
These and other features and advantages of this invention are described in or apparent from the detailed description of various exemplary embodiments of the systems and methods according to this invention.